SANTA CLARA — To John Carlos, it all looks so familiar. A national anthem. An act of defiance. A firestorm of outrage and debate.

In 1968, it was Carlos and teammate Tommie Smith raising gloved fists on the medal stand at the Mexico City Olympics.

In 2016, it’s 49ers quarterback Colin Kaepernick sitting during the national anthem to make a statement about civil rights.

Carlos, 71, is happy to welcome Kaepernick to the club.

“I would let him know that he’s involved in a movement. He’s jumped into the pool of human history,” Carlos, the San Jose State alum, said by phone Monday from his home near Atlanta. “(He’s) with those that have prevailed and risen above the norm.”

Kaepernick launched a nationwide debate by refusing to stand for the national anthem at 49ers games because “I am not going to stand up to show pride in a flag for a country that oppresses black people and people of color.”

In doing so, the player once touted as a new-age quarterback has set off an old-school debate: Should athletes use the playing field as a political arena? Where is the separation between sport and state?

Kaepernick’s rebellion was rare enough in the modern age to lure some bygone civil rights crusaders back into the headlines: Jim Brown, Kareem Abdul-Jabbar, Carlos, Smith and other long-ago athletes are suddenly revisiting the same issues they addressed in the 1960s.

It’s like an old-timer’s game, but with activists.

“What should horrify Americans,” Abdul-Jabbar wrote in a column for the Washington Post, “is not Kaepernick’s choice to remain seated during the national anthem, but that nearly 50 years after Ali was banned from boxing for his stance and Tommie Smith and John Carlos’s raised fists caused public ostracization and numerous death threats, we still need to call attention to the same racial inequities. Failure to fix this problem is what’s really un-American here.”

But even athletes are divided on the question about when it’s appropriate to speak out. In an interview this week with The Undefeated, boxer George Foreman held firm to his belief that sports and activism are a bad mix. Back at the ’68 Olympics, as an answer to Carlos and Smith, the boxer celebrated his gold medal by walking around the ring holding a small American flag.

“Sports is free. It’s when the whole world can come together and compete,” Foreman told The Undefeated. “(Some) athletes don’t know what they’re talking about and don’t even know what they are standing for. They just have someone in their ear. … So I don’t like it, and I never did like it.”

Eric Byrnes, the former A’s outfielder, reacted to Kaepernick’s methods by taking to social media. Pointedly, Byrnes posted a photo of a different kind of athlete-activist: his late friend, Pat Tillman, the former Leland High School star who abandoned his NFL career in the aftermath of the Sept. 11 terrorist attacks.

Tillman enlisted in the U.S. Army and died in the mountains of Afghanistan in 2004.

Byrnes, when asked to elaborate via email, responded with an impassioned essay called, “Why I Stand,” which he later posted in full on his website (byrnes22.com).

In his written response, Byrnes encouraged Kaepernick to take action off the field — through outreach programs, public speaking and community forums — but to avoid something as intentionally divisive as sitting through “The Star-Spangled Banner.”

Byrnes wrote: “The national anthem was and still is a time I am able to stand up, place my right hand over my heart, bow my head and show gratitude for the sacrifices others have made for me to be able to play or watch a GAME that I love.”

To Carlos, though, there is no better forum for taking a stand than when the spotlight is shining brightest. When Carlos won bronze and Smith won gold in the 200 meters in Mexico, they used the ensuing national anthem as a chance to raise their black-gloved fists as a gesture on behalf of human rights.

It sparked worldwide controversy and dialogue, which was exactly the point.

Carlos said it shouldn’t matter that Kaepernick has a base salary of $11.9 million for this season. The Olympian said Kaepernick can still speak on behalf of the oppressed.

“Who’s speaking for them if he doesn’t speak for them? He’s a noted figure, a public figure,” Carlos said. “If he makes a statement, then a certain collective group of people in the NFL will pay attention to what he’s saying.

“Whether they agree or disagree, the process is for them to start having some discussions and dialogues over the dinner table. They need a discussion over how we can resolve these issues.”

Carlos was 23 years old at the time of his protest. He later wrote that “as soon as we raised our hands, it was like somebody hit a switch. The mood in the stadium went straight to venom.”

Within days, both track stars were suspended from the U.S. team and sent home from Mexico City. Carlos said the next 10 years were a personal hell. People walked away from him, mostly because they were fearful of being ensnared by the controversy. His marriage crumbled.

But over time, Carlos became to be viewed as a civil rights icon. In 2008, he and Smith won the Arthur Ashe Award for Courage.

“Everyone wants to be associated with the legacy and associated with history,” Carlos said. “But where were you when I needed you to lend support to me when they were chopping my legs out from under me? That’s the question.”

For that reason, Carlos is strong in his support of Kaepernick. He praised him for continuing in the tradition of those famous raised fists at the ’68 Olympics. “We were the gardeners: We planted the seeds. And now what you’re seeing with these young individuals is the fruit of our labor.”

Kaepernick, like Carlos, has endured a swift and harsh reaction, with everyone from Republican presidential candidate Donald Trump to his old coach Jim Harbaugh questioning either the message or the method.

But Kaepernick said has he was prepared for the repercussions. That, too, is something Carlos can understand.

“You think Harriet Tubman didn’t think about backlash when she built the underground railroad?” he said. “You think Rosa Parks didn’t think there would be a backlash when she sat on that bus?

“Everyone thinks about backlash. But backlash has to take a second seat to what the overall circumstances are. … He’s not worried about the repercussions coming to him any more than me worrying about the repercussions coming 48 years ago.”